A number of such rotors with laminated sheets arranged thereupon are known in the prior art, most of which regard sheets which, more or less extensively, are punched stacks. These rotors are used in asynchronous machines and in permanent magnet synchronous machines. Regarding rotors known in the prior art, additional elements are often used in producing a reliable connection for transmitting torque between the lamination stacks and the shaft, such as axial tie rods, positive locking means, or other helpful means, such as glue.
There are also joining techniques known, in which the lamination stack is held onto the shaft via an interference fit. Thermally shrinking the lamination stacks is also known, whereby the shaft is cooled and the lamination stack accordingly heated. This thermal joining, however, is cumbersome and involves a great expenditure of energy and time. In addition, problems occur with condensation, which can build up due to temperature differences in the joining region. Furthermore, joining methods are known, in which lamination stacks are simply mechanically pressed onto the shaft. The application of pressure, however, requires that the lamination stacks be highly stable, which is not so with lamination stacks that are merely punched. Instead, regarding this sort of mechanically joined interference fit, lamination stacks are used which have been laminated with baked enamel, thus forming a stable structure. For stacks of this kind, the mechanical joining is further augmented by the adhesive properties of the baked enamel.
Furthermore, for example, a rotor is known from DE 10 2007 039 186, in which the lamination stack is slid onto the support element and arranged between the facing compression rings, whereby the compression rings are braced against one another by a bolted tie-rod and shrunk onto the shaft, or are attached to the shaft using some other type of rotation-resistant shaft-hub connection. In this case, a high degree of production cost and effort is needed in order to correctly establish the connection of the compression rings with the shaft on the one hand, and, on the other hand, their tension against one another.
Rotors of elaborate design are disclosed in DE 1950 586, in which the lamination stack is braced tightly between two nuts screwed onto the shaft. As a result of the tension of the lamination stack with respect to the shaft, a high degree of bending stiffness is achieved for the rotor. In order to compensate for the thermal expansion of the lamination stack, additional elastic elements are described, which are arranged between the lamination stack and the nuts. A similarly conceived rotor is known from JP 2005184957, whereby, in this case, axial grooves in the shaft are provided, in which the lamination stack is seated via corresponding protrusions.
Frictional press-fit connections for lamination stacks are also known, for example from DE 10 2011 012 429, in that case to a hollow shaft. These have the disadvantage that the electromagnetic effect of the sheets is impaired at the joining diameter. In addition, stresses on the connections joined on the inside diameter of the lamination stack via interference fit act to impair material properties and consequently the function of the electromagnetic sheet.
Regarding the design of rotors for synchronous machines, it should be generally noted that permanent magnets, which consist of brittle material, are embedded into the lamination stack and can sustain damage due to stresses from the interference fit.